Neovascularization associated with diabetes is the leading cause of new blindness in people age 2-74. To prevent and treat neovascular disorders such as diabetic retinopathy more effectively, there is a clear need to develop a better knowledge of angiogenesis at the cellular and molecular levels. The applicant states that the long-term goal of his research program is to understanding the sequence of events that occur when normally quiescent vascular endothelial cells (EC) differentiate into a proliferative, angiogenic phenotype. The study proposed in the application will focus on a nuclear RNA binding protein named pigpen that appears to lie directly in the pathway of these events. EC pigpen was first isolated in the applicant's laboratory by its affinity for polysaccharides. The applicant reports that expression of this nuclear lectin is sharply regulated during EC phenotype transition. Recent experiments have shown that vascular endothelial growth factor (VEGF) treatment of EC triggers a redistribution of pigpen, that pigpen antagonists block VEGF-stimulated proliferation, and that pigpen may play an essential role in RNA metabolism during EC proliferation. The first aim of this project is to establish a function link between VEGF and pigpen. The second aim will be to identify pigpen-binding transcripts and determine if they represent EC-specific or ubiquitous genes. The applicant states that, in preliminary work, his group has isolated and cloned a population of pigpen-binding RNAs from proliferating EC. This library will be analyzed using standard sequencing techniques and nucleic acid databases. The applicant proposes a third aim to test the hypothesis that pigpen plays a role in RNA biogenesis during EC proliferation. A series of pigpen antagonists will be microinjected or transfected into cells. Northern analysis and in situ hybridization will then be used to track the synthesis, processing, and transport of specific transcripts in treated and control cells.